The death toll wrought by Hurricane Katrina is expected to surge into triple figures today as authorities in Mississippi, Louisiana, Florida and Alabama struggle to cope with the aftermath of what may be the worst natural disaster in US history.
There were unconfirmed reports of at least 80 deaths in Mississippi where scores of homes were obliterated by the force of the storm. In Louisiana, there were reports of bodies floating in the water and an emergency morgue was set up in the worst-hit district of New Orleans, the 9th Ward.
US officials said hundreds of people may have died in the hurricane, which sent a wall of water into Mississippi and flooded New Orleans.
"It's going to be in the hundreds," Biloxi city spokesman spokesman Vincent Creel told journalists. "
"Camille was 200, and we're looking at a lot more than that," he said, referring to Hurricane Camille, which hit the area in 1969 and destroyed swaths of Mississippi and Louisiana, killing a total of 256 people.
New Orleans Mayor Ray Nagin reported bodies floating in the city's floodwaters.
The hurricane is expected to be one of the most expensive in US history in terms of the damage caused, with insurance costs predicted to rise up to $26 billion.
There was a serious levee break as dawn broke over New Orleans, causing water to continue to rise up to 20 feet and submerging 80 per cent of the city. A state of martial law was later declared in the city.
As the clean-up operation began, New Orleans Mayor Ray Nagin said he had a "heavy heart" and little good news for residents. "We have just about everyone you can think of out there trying to rescue individuals from their roofs," he said.
"We have an incredible amount of water in this city, both airports are under water, we have an oil tanker that has run aground and leaking oil, we have houses that have been literally picked up off their foundations and moved."
More than a million homes from Louisiana to Florida were left without power, and authorities said it could be two months before electricity is restored to everyone.
Emergency workers said they could hear people screaming for help from the rooftops but had no way to reach them. Many of those stranded smashed their way out using axes.
Dozens of residents move to higher ground in New Orleans as rising waters flood neighborhoods
The official death toll jumped sharply late last night when an emergency centre in Harrison County, Mississippi said an estimated 50 people had died in the county, with at least 30 dead at one beach-side apartment complex in the city of Biloxi.
The American Red Cross said its response was the organisation's largest yet to a natural disaster.
Some 40,000 people sought refuge in shelters across Mississippi and Louisiana, and volunteers urged residents to stay away from their homes for as long as possible.
Several observers described the ravaged areas as "war zones," where hundreds of residents lost everything and hurricane winds blasted windows and turned entire streets into lakes. One woman said all she had managed to retrieve from her home was a shoe.
The US coastguard said several helicopters had moved in over rooftops trying to reach those stranded on submerged streets.
Ten major hospitals in New Orleans were running on emergency back-up power.
The federal government began rushing baby formula, communications equipment, generators, water and ice into hard-hit areas, along with doctors, nurses and first-aid supplies.
Oil refiners said damage to their equipment in the Gulf region appeared to be minimal, and oil prices dropped back from the day's highs above $70 a barrel.
But the refiners were still assessing the damage, and government said it would consider releasing oil from the nation's emergency stockpile if necessary.
Katrina moved through the Gulf of Mexico as a 175-mph Category 5 storm - the most powerful ranking on the scale. But it weakened to a Category 4 and made a slight right-hand turn just before it came ashore around daybreak yesterday, passing just east of New Orleans.
The city has not been hit directly by a major storm since Category 3 Hurricane Betsy struck in 1965.